The present invention relates to a method of conveying or transferring a sheet material through a working apparatus. More specifically, the invention relates to a method of transferring a sheet of wood veneer through a hot press type drying apparatus.
There has been known a veneer dryer having a pair of hot plates which are disposed one above the other for drying a sheet of wood veneer by hot pressing the sheet therebetween. In such dryer, a green or undried veneer sheet is moved from one end of the dryer to a predetermined position within the dryer, where the veneer sheet is hot pressed for a predetermined length of time for drying to a desired extent. After the drying has been completed, the dried veneer sheet is moved out of the apparatus through the opposite end thereof.
For better understanding of underlying problems and objects of the invention, reference will be made to FIGS. 24 to 27 which show a typical hot press type veneer dryer. It is to be understood that in describing the drawings only those portions of the construction of the dryer has been shown which enable those skilled in the art to readily understand the underlying principle and concept of the present invention.
Referring to FIG. 24 which is a schematic side view of the hot plate dryer and FIG. 25 which is a fragmentary plan view as seen from dash-and-dot line Axe2x80x94A in arrow direction, a pair of hot plates 101, 103 are disposed one above the other, of which the lower plate 101 is stationary while the upper plate 103 is movable toward and away from the stationary lower plate 101, as indicated by arrow. Seen in the direction in which veneer sheets are transferred through the dryer, or from right to left as viewed in the drawings, the hot plates 101, 103 have a longitudinal dimension L1, respectively, corresponding to the maximum working length of the dryer, while each veneer sheet 115 to be worked by the dryer has a longitudinal dimension L2 as measured in the same direction, and this L2 is smaller than L1, as best seen FIG. 26.
Adjacent to the upstream end, or right hand side as seen in FIG. 24, of the hot plates 101, 103 is located a plurality of feed rolls 105 mounted on a common drive shaft and rotating constantly in the arrow direction for moving a veneer sheet 115 into the dryer. On the opposite downstream end of the apparatus is provided a plurality of pairs of delivery rolls 107 mounted on drive shafts, respectively, of which the lower rolls are constantly rotatable in the arrow direction, while the upper idle rolls 107 are spaced apart from their corresponding lower rolls at an appropriate distance for holding therebetween and conveying a dried veneer sheet out of the dryer.
As shown in FIG. 25, a veneer sheet loading device is provided on lateral side of the dryer adjacent to the feed rolls 105, which includes an arm 113 reciprocally swingable about a pivot 111 and having at one end thereof a pusher 109. The arm 113 is normally located in its inoperative position as indicated by solid line and swingable by means of any suitable actuator such as pneumatic or hydraulic cylinder to its operative positions 109a and 109b indicated by phantom lines, respectively. Though not shown in FIG. 25, a similar device including an arm 113 and its related parts is located on the opposite side of the dryer in a symmetrical relation with respect to longitudinal center line (not shown) of the dryer. These two loading devices on opposite sides of the apparatus are operable in a synchronous manner for placing an undried veneer sheet to a predetermined position within the apparatus and also moving a dried veneer sheet partially out of the apparatus, as will be explained below.
In operation, a sheet of green veneer 115 is conveyed by the feed rolls 105 toward the dryer and inserted between the hot plates 101, 103. Movement of the veneer sheet 115 is stopped when the trailing end of the sheet 115 has just moved past the feed rolls 105 as shown in FIGS. 24, 25 and, therefore, conveying action of the rolls 105 is imparted to the veneer sheet 115 no more. As shown in FIGS. 24, 25, the veneer sheet 105 is partially inserted between the hot plates 101, 103 with part of its trailing end portion lying outside the hot plates 101, 103. Subsequently, the loading devices are actuated simultaneously to swing the arms 113 inward, or counter clockwise direction as seen in FIG. 25 for the arm 113 illustrated in FIG. 25 and opposite direction for the similar arm 113 (not shown) located on the opposite side of the dryer. By so doing, the pushers 109 are swung into contact with the trailing end of the veneer sheet 105, then moving the sheet along the upper surface of the stationary hot plate 101. The arms 113 are turned until the pushers 109 reach position 109a, where the veneer sheet 115 lies well within the working area or the longitudinal extension of the hot plates 101, 103 as shown in FIG. 26. After the veneer sheet 115 is thus positioned in place between the hot plates 101, 103, the arms 113 are swung back to their original position shown in FIG. 25, and the upper hot plate 103 is lowered as indicated by arrow in FIG. 26 to press and heat the veneer sheet for a predetermined length of time for drying.
After drying of the veneer sheet 115 has been completed, the upper hot plate 103 is elevated as shown in FIG. 27 and the arms 113 are swung again then to position 19b to move the dried veneer sheet 115 from the position of FIG. 26 to a position shown in FIG. 27 where the leading end of the sheet 115 can be caught and held by the delivery rolls 107. Thus, the dried veneer sheet 155 is conveyed by the delivery rolls 107 out of the dryer to any subsequent working station (not shown).
As understood by those skilled in the art, the presence of the sheet loading equipment inevitably complicates the veneer dryer and hence increases its manufacturing cost. Furthermore, addition of such devices require troublesome maintenance and therefore additional cost.
Accordingly, an object of the invention is to provide a method of transferring a sheet such as wood veneer sheet through a working apparatus which dispenses with the above-described veneer sheet loading equipment or similar devices.
According to the invention, a working apparatus in which a method of the invention is performed has a working area with a dimension L1 as measured along the direction in which the sheet is transferred, while a sheet to be transferred through the working apparatus has a dimension L2, as measured along the same direction, which is smaller than the dimension L1. The working apparatus includes feed means in the form of rotatable rolls disposed adjacent to one end of the working area and capable of moving the sheet partially or incompletely into the working area with part of the trailing end portion of the sheet lying outside the working area and delivery means such as rotatable rolls disposed adjacent to the opposite end of the working area of the working apparatus for removing the sheet therefrom.
In such working apparatus, a first sheet is moved by the feed means partially into the working area. Then, a second sheet is moved by the feed means into abutment of the leading end thereof with the trailing end of its preceding first sheet and moved further thereby to cause the second sheet to push its preceding first sheet to a predetermined position within the working area. When this position has been reached by the first sheet, the feed means is stopped and then reversed to move back the second sheet out of the working area. After the first sheet has been thus positioned in place within the working area of the apparatus and the succeeding sheet has been moved clear of the working area, the apparatus is operated to work the first sheet, for example, by pressing. The feed means is activated again to move the second sheet into abutment with the trailing end of its preceding worked first sheet and moved further while allowing the second sheet to push the first sheet toward the delivery means. The second sheet is moved to a position to which the first sheet was previously moved by the feed means, while the first sheet is removed by the delivery means out of the working area of the apparatus. Such steps of operation is repeated to transfer a series of sheets successively through the working apparatus. Since a sheet fed into the working apparatus incompletely can be moved by another sheet that follows to a predetermined position within the working area, loading equipment as described above with reference to prior art apparatus may be dispensed with.
According an embodiment of the invention, the step of reversing the feed means to move back the second sheet out of the working area may be omitted. For example, after a first sheet has been moved partially into the working area, it may be worked as it is with part of its trailing end portion lying outside the working area if such working is acceptable. The worked sheet can be removed by moving a second sheet by the feed means into abutment of the leading end thereof with the trailing end of its preceding worked first sheet and further to a position to which the first sheet was previously moved by the feed means, while causing the second sheet to push the first sheet toward the delivery means.
In still another embodiment, a first sheet fed incompletely into the working area is moved by being pushed by a second sheet to a predetermined position within the working area of the apparatus. Then, working by the apparatus may be done for the entire of said first sheet and part of the leading end portion of the second sheet which then lies within the working area. By so doing, the step of reversing the feed means may be omitted. The second sheet is moved by the feed means to a position to which the first sheet was previously moved by the feed means, so that the first sheet is pushed to move toward the delivery means, which then removes the sheet from the working apparatus.
Additionally, the working apparatus may include aligning means in the form a stop member disposed between one end of the working area and the feed means and extending perpendicularly to the extension L1 of the working area of the apparatus for aligning or orienting each sheet straight with respect to the direction in which the sheet is moved by the feed means. In such a case, method of the invention further comprises a step of aligning each sheet by the aligning means before it is moved by the feed means into the working area.